Marine underfeed stoker



Filed Sept. 25, 1930 5 Sheets-Sheet l 1933- H. E. PRESTON wmsw MARINE UNDERFEED STOKER Filed Sept. 25, 1930 5 Sheets-Sheet 5 i iOW/Zy 0a. 17, 1933. H E, PR T'ON 1,930,909

MARINE UNDERFEED STOKE-R I Filed Sept. 25, 1930 5 Sheets-Sheet 4 LI .4 a

ksflzzar Oct. 17, 1933. H. E. PRESTON I 1,930,909

MARINE UNDERFEED STOKEH Filed Sept. 25, 1950 s Sheets-Sheet 5 j 720.5%1" Ererig H6659),

Patented Get 17, 1933 ljl ii'ltlfi STATES FATE MARINE UNDERFEED STOKER Application September 25, 193i) Serial No. 484,425

3 Claims.

The principal object of this invention is to provide a mechanical stoker of the underfeecl type which reason of novel structural and me- .-lcal shall meet all the requirements and be well adapted for use on vessels and under similar conditions involving a relatively restricted space and limited available head room.

To this general end, an object of the invention is to provide a marine underfeed stoker characterized by a materially stee, er inclination of combustion grate than has been found practicab e prior to my invention'the efficiency of the stoker being correspondingly increased, all as hereinafter more fuily described.

Another object of the invention is to provide marine underfeed inclined-grate stoker having means tending to stabilize the fuel bed and to prevent displacement or cascading of the fuel from te grate, due to movements of the boat in rough weather, said means making practicable the use of a grate of relatively steep inclination, as set forth above.

A further object of the invention is to provide a marine stoker of the stated type having a novel form of ash discharge device, insuring stability of the fuel bed under adverse weather conditions and precluding possibility of the cascading of the fuel bed from the grate during discharge operations.

More specifically, an object of the invention is to provide a marine stoker of the stated type including a crusher r011 affording a continuous stabilizing support for the fuel and a continuous ash discharge free from the dangers of fuel bed displacement mentioned above.

To these same ends, the invention contemplates the provision of a novel ash pit construction so designed as to make practicable within the necessarily limited available space the use of suitable grinding apparatus for the fuel refuse, said apparatus constituting a highly desirable and even essential adjunct of the refuse disposal system and being of particular importance in conjunction with certain types of ash conveyers and ejectors commonly used on marine vessels.

A still further object of the invention is to provide a novel ash discharge device of a character well adapted for marine stokers.

More specifically, the invention provides an improved ash pit construction in which a crusher roll or its equivalent functions not only to reduce the clinkers and large particles of the fuel refuse to a desirably fine condition, but also as a means for discharging the refuse from the ash chamber, the novel arrangement by reason of extreme compactness rendering the crusher principle available in marine stoker practice and also actually effecting a material ovement in the refuse disposal system per se. 7

A further object of the invention is to provide 6o a novel ash pi structure of the stated character that shall be substantially self-sealing.

A still further object of the invention is to provide a stoker of the stated character comprising a crusher roll actuated from the main stoker drive mechanism.

To this general end, a specific object of the invention is to provide a stoker of the stated type in which th drive mechanism for the fuelfeeding elements is so relatively arranged with respect to the stoker structure as to offer little or no interference with the passing of fuel from the normal firing floor to the stoker hoppers.

Still another object of the invention is to provide a marine stoker having a novel fluid-cooled rear wall insuring a properly unobstructed movement of ash from the grate to the ash pit.

Another object of the invention is to provide a stoker of the stated type in which the fuel-feeding elements are independently adjustable as to stroke 9, and relative to each other, and in which the said adjustments may be effected largely from the front and externally of the stoker.

Still another object of the invention is to provide a stoker having novel means for inspecting the interior of the stoker from the front thereof.

A further object of the invention is to provide novel and improved means for mounting the mechanical stoker in the boat. 7

The invention further resides in certain novel 9o structural features and mechanical details hereinafter more fully set forth and illustrated in the attached drawings, in which Figure 1 is a side elevational view of a stoker made in accordance-with my invention;

Fig. 2 is a front view, more or less diagrammatic, of the interior portions of the stoker;

Fig. 3 is a rear elevational view of the stoker;

Fig. 4 is a more or less diagrammatic side elevational view illustrating the crusher-operating loo mechanism;

Fig. 5 is a plan view of the crusher operating mechanism, and

Fig. 6 is a section on the line 6-6, Fig. 4.

Heretofore mechanical stokers employed in marine vessels have been subject to certain undesirable structural restrictions, due to the condition under which the stokers must be installed and operated. The space available for installation, for example, is necessarily limited, particu- 11-0 larly as to head-room, while the movements of sea-going vessels require certain limitations not present in land installations. I have discovered that crusher roll mechanism used in conjunction with mechanical stolrers as hereinafter set forth has particular advantages and novel functions in marine installations and is capable of compensating to a material extent for the various operating and structural limitations imposed by marine conditions.

It has been customary in marine installations of underfeed stokers of the type involving an inclined grate to employ a grate inclination of undesirably low pitch, this being dictated in part by a lack of available head-rooin and partly by the danger of the lurching movements of the vessel cascading the fuel from the grate. Also dictated to some extent by lack of available headroom has been the use in marine installations of dump plates overlying the ash pit. which pf are periodically lowered to deposit the ashes into the pit. This type of disposal system also ecessitates a relatively low inclination of the combustion grate, due to the fact that when the said plates are lowered, a sudden lurch of the vessel may easily result in a cascading of the entire or major portion of the fuel-bed from the grate directly into the ash pit.

In accordance with my invention, I provide the Stoker with an pit so designed as to permit the use of crusher mechanism which functions not only to continuously support the fuel-bed but to discharge the ashes and refuse at a rate cor esponding substantially to the rate of movement of the fuel upon the combustion grate, said crusher mechanism entailing no increase in the overall vertical dimensions of the stokcr assembly. The continuous support for the fuel-bed precludes the possibility of accidental dislodgment of the fuel from the combustion grate and makes practicable a relatively steep angle of inclination of the combustion grate with a resulting increase in the efficiency of the combustion operation. By utilizing my invention, grate inclinations of twentydegrees or more have been found satisfactory. The use of crusher mechanism in accordance with my invention also renders available in marine installation all the many advantages of this system as previously applied to land installations.

By the present invention, therefore, I provide a stoker meeting all the rigid requirements of marine usage and at the same time incorporate certain features, such as ash crushing means, which while particularly desirable in a marine stoker, as set forth above, has heretofore been considered impracticable or unsuitable.

With reference to the drawings, the stoker comprises the usual inclined alternately arranged tuyere and stoker sections designated respectively 1 and 2, the retorts terminating at their lower ends upon movable extension grates 3, from which the ash and refuse fall into a pocket d. This pocket, in accordance with my invention, is pro vided with a crusher roll 5. Fuel is fed into the retorts 2 from a hopper or hoppers 6 by a series of rams '7, one for each of the hoppers, these rams operating in ram cylinders 8 with which the said hoppers 6 are in communication. Fuel is fed by reciprocation of the rams onto dead plates 9 constituting the upper floor portions of the retorts, and is advanced in the lower portions of the retorts through the medium of secondary fuel rains or pushers 11 which operate elow the rear edges of the dead plates 9, see Fig. 1. The'pushers 11 feed the fuel rearwardly in the lower portion of the hopper upon a lower dead plate 12, the inner or rear edge'of which overlies the extension grate 3.

It will be noted that the entire stoker structure is supported upon the tank top 70 through the medium in part of the boiler columns (not shown) The rear or inner end of the stoker is supported directly from the said tank top through the medium of uprights 71, while the forward or outer end of the Stoker is supported from a transverse beam 72, the opposite ends of which are supported in the aforesaid boiler columns (not shown), the latter resting upon the tank top 65, as a base.

In accordance with my invention, the mechanism for actuating the main ram '7, the pusher ll the extension grate 3 is located in its entirety below the b r: and in such manner as to offer no interference to the feeding of fuel by the usual methods from the firing floor, designated by the reference numer l into the hop strated in Figs. 1 and 3, the ran1- an comprises a motor la mount- 'escnt instance upon the floor l3 and a reduction-gearing power-box 15, preferably of the variable speed type, connected with the motor i l th ough a chain belt 16 and a shaft 17 suitably journaled the front of the stoker. The driven shaft 18 of the power-box 15 comprises a series of cranks 3.9 respectively connected through rods 21 with the main rams 7. It will be noted by reference to F 1 that the entire power mech anism as described above lies well below and under the hoppers 6 in a position offering a miniobstruction to the free passage of fuel from the firing floor 13 into the hoppers, and I provide a covenplate 22, see Fig. l, which overlies the power mechanism. closes the space intervening between the front under side of the hoppers and the said mechani whereby fuel failing to enter the hopper 6 is prevented from falling downwardly into the said operating mechanism. The plate or plates 22 are removable to afford ready access to the mechanism required.

Each ram cylinder 8 has at its forward end a depending flange 23, through which flange extends a rod 2 which also passes through a rear cylinder flange 25 and the front wall 26 of the stoker and is attached to the pusher 11. of the rams 7 has at its forward or outer end a depending arm 2'7 having an opening through which the rod 24 freely passes, and lost motion between the said rod 24 and the rain is regulated, or entirely eliminated, through the medium of a block 28, adjustable on the forward end of the said rod and having in the present instance a set screw 31 by means of which the block may be socured in any desired adjusted position, the dis tance between the block 29, and a fixed armabutting shoulder 28 on the rod determining the extent of the lost motion. By adjusting the block 29 longitudinally of the rod therefor, the stroke of the rod may be regulated as required.

At its inner end a reduced extremity of the rod projects freely through an opening in the end of the pusher 11, and a plurality of washers 32 are provided may be applied to the innor end of the rod to thereby regulate or eliminate the lost motion between the rod and the pusher 11, this affording a still further adjustment solely affecting the stroke location in the retort of the pusher 11.

Each of the rods 24 carries externally of the stolrer a depending arm 33 having at its lower end an opening for reception of a rod 34 which. extendsinwardly through the front wall of the Each stoker to the corresponding section of the extension grate 3. The rod 34 has a collar 35 constituting an abutment for the arm 33, and the outer extremity of the rod is adapted for reception of horseshoe or other suitable detachable washers 36 by means of which lost motion between the arm 33 and the rod 34 may be regulated to thereby control the length of the stroke of the said rod and of the extension grate 3. It will be noted that the block 29 and washers 36 aifords individual or relative adjustment of the pushers 11 and the extension grate 3 from the exterior of the stoker, and that additional individual adjustment of the pusher 11 is afforded by the washers 32.

Combustion air is supplied to the tuyeres 1 from an chamber 87 underlying the stoirer, and passage of air from this chamber to the extension grate 8 and to the under ying lower wall grate 38 is controlled by a damper so designed that siftings collecting in the secondary air chamber 41 are discharged. when the said damper 39 is opened. The damper is carried by a shaft i2 operative from the exterior of the stoker through a hand lever 43, and when closed, as shown in Fig. 1, forms a hopper-like pocket in th chamber 41 underlying the extension grate. Siftings entering this chamber 41 collect in the pocket and are dumped into the bottom of the main air chamher when the damper is opened.

As previously set forth, the ash pocket 4 is provided with a crusher roll 5 which is adapted to rotate in the direction indicated by the arrow in Fig. 1 and which cooperates with a crusher apron composed in the present instance of a plurality of plates 46 suitably mounted in the front wall of the ash pocket below the grate 38 to grind or break up the clinkers and to carry the latter into the bottom of the pit. Below the crusher roll 5. the ash pocket is terminated by a curved plate 47 which curves downwardly and rearwardly on an arc corresponding more or less to the circumferential arc of the crusher roll.

This plate is so designed and located with respect to the roll 5 that the latter in addition to its crushing function effects a discharge of the ashes from the pocket and into an ash pit '76 disposed to the rear of the stoker. A rear crusher apron 48 is also provided which preferably is adjustable rearwardly to permit use of a bar or the like to break up clinkers in the crusher pit when this is necessary or desirable. The adjustability of the apron 48 also aids in quick removal of the refuse from the pocket in the event that this should be required.

The ashes in the pocket accumulate above the crusher roll and by filling the spaces between the roll and the aprons 46 and 48 and the plate 47 form an effective seal substantially excluding air from the ash pocket except as introduced through the grate 38. The upper surface of the substantially horizontal portion 74 of plate 47 coincides with the floor '75 of ash pit '76 disposed to the rear of crusher roll 5, thus forming a substantially horizontal passage '77 through which the ash is discharged.

use in marine and like stokers a crusher apparatus of high efficiency, but actually effect a conservation of head room in the stoker as a whole.

Many other advantages are obtained by the use of the crusher apparatus as described. It will be noted, for example, that the crusher roll constitutes a continuous support for the fuel bed, and that it accomplishes removal of the ashes without in any way affecting this support. quence, the entire fuel bed is rendered highly stable and the danger of the cascading of the fuel from the grate always present in installations in-' volving the use of dump plates is entirely eliminated. As previously set forth, elimination of this tendency of the fuel to cascade from the grate during the ash dumping operations makes possible the utilization of a grate having a considerably steeper inclination than hitherto has beenfound practicable, with the result that the efliciency of the stoker is materially increased.

Where steam-jet and similar conveyors are used, as is frequently the case in marine practice, it is highly important that the clinkers and larger refuse be reduced to small sizes.

In order to insure a free and unobstructed passage of ash to crusher roll, I prefer to provide the rear wall of the furnace with a suitable fluid cool ing system, such as that illustrated in Fig. 1. This system comprises a duct 65 through which air is passed to a series of channels 66 formed in the rear wall 67 of the furnace. The channels 66 empty into a duct 68 which in the present instancecarries the air .to the air supply chamber 37from which it passes to the fuel bed. Cooling of the wall in this manner prevents accumulations of slag and clinkers and insures unobstructed passage of the refuse to the crusher. Cooling systems employing a cooling medium other than air may be utilized if desired.

The crusher roll 5 receives its actuation from the stoker crank shaft 18 through the medium of a connecting rod 49, which connects at its upper end to a crank 50 on the extremity of the said crank shaft and at its lower end to a bifurcated lever 51, which lever is pivotally mounted for free movement upon the projecting end 52 of the crusher roll shaft. This shaft also carries on its projecting end a pair of ratchet wheels 53, which wheels are fixed to the shaft and adapted to be operatively engaged by a pawl 54 pivotally mounted between the arms of the lever 51, the pawl engaging both of said ratchet wheels and extending across the intervening space. Within this space and loosely mounted upon the shaft 52 is a cam 55, a portion or portions of which project beyond the peripheries of the ratchet wheels, and this cam is adjustable to various positions through the medium of a hand lever 56 located preferably in an available position on the firing floor 13. The lever56 is connected with the said cam through the medium of a suitably supported and journaled shaft 59, to a projecting arm 60 of which the lever 56 is connected through a rod 61. At its inner end, the shaft 59 has a second arm 62 which is connected through a link 63 to the cam.

From the foregoing description, it will be apparent that by adjusting the cam 55 to different positions around the shaft 52, the effective stroke of the pawl 54 may be varied as desired.

This device affords a highly flexible control of the intermittent rotation of the crusher roll.

By the above described construction, I have provided an extremely compact and efiicient stoker of the underfeed type, the head-room of which is reduced to a minimum and which in all As a conse- 1 respects is Well suited for use on vessels or under similar conditions. It will be understood, of course, that there may be minor modifications in the structure as a whole and in the various individual mechanical parts without departure from the invention.

I claim:

1. In a stoker, the combination with a grate structure, an ash pocket located at the end of said grate and having front and rear walls, an ash pit located to the rear of said pocket, the front wall of said pocket terminating at its lower end in a curved plate having a substantially horizontal portion in alignment with and forming a continuation of the floor of said ash pit, said rear wall terminating upwardly from said floor forming a substantially horizontal discharge passage, a crusher roll mounted near the bottom of said pocket in operative relation with said curved plate and means for rotating said roll in a direction whereby the roll coacts with said curved plate to positively propelthe crushed refuse horizontally through passage.

2. In a Stoker, the combination with a grate structure, of an ash pocket operatively associated with said grate, said pocket having front and rear Walls, an ash pit disposed laterally from said pocket adjacent the bottom thereof, one of said walls terminating above the floor of said pit and defining a passage connecting said pocket with said pit, the other and opposite wall of said pocket terminating in a curved section near the lower end thereof and having a substantially horizontal portion in substantial alignment with and forming a continuation of the floor of said pit, crusher aprons mounted in both of said walls of said pocket, a crusher roll mounted near the bottom of said pocket in operative relation with said aprons and said curved section, and means for rotating said roll in a direction whereby the roll coacts with the aprons to crush the refuse, and with the curved section to positively propel the crushed refuse horizontally through said passage.

3. In a stoker, the combination with a progressive feed grate structure, of means forming an ash pocket comprising front and rear walls, said front wall abutting the discharge end of said grate and including a crusher apron and an arouate-shaped plate extending downwardly from said apron and curving rearwardly and terminating in a substantially horizontal portion beneath said rear wall and defining therewith a discharge opening, an ash pit disposed to the rear of said pocket having a bottom wall in substantial alignment with the horizontal portion of said plate and forming a substantially horizontal passage, a crusher roll mounted in operative relation with said apron and said plate, and means for rotating said crusher roll towards said apron and said plate whereby the roll ccacts with the apron to effectively crush refuse therehetween and with the plate to positively propel the crushed refuse through said horizontal passage.

HERBERT E. PRESTON. 

